"Various (BlackRock, Inc.) Persons" apparently bought a total of 19.6 million shares (5.46%) The "event" (SEC's word for it) occurred on 12/31/2010, and was reported to SEC on 1/21/2011. Not exactly a "just buy" - rather a "just now publicly known". I didn't see anything until you posted today.
BR is affiliated with BR Institutional Investors, which already owned 8.6 million shares, and with Barclays (which as of 3/31/09, was top dog with only 26.2 million shares. Barclays "appears" to have flown the coop (de grace?).
It's Musical Chairs at the institutional level. Somebody buys, somebody sells. But without the public's TIMELY knowledge.
If you happen to be involved someplace in the financial business where inside information has a way of ending up, or if you have the right inside job with a client, it's almost impossible to lose money. If you don't believe it, just get to know any Masco insider - or any of Masco's financial business friends.
Until the Ancient History folks at the SEC get the numbers out, a lot can happen.
For example, as of 6/30/10, holder number one was Fidelity with 35.2 million shares and holder number two was Capital World with 28.6 million shares.
At the end of the following quarter, 9/30/10, Capital World held 34.1 million, and Fidelity 27.5 million.
Go figure. The shares Blacrock bought were sold by somebody (somebodies). Who did the selling may be revealed when institutions eventually get around to reporting their 12/31/2010 positions. Print out the current holdings and compare when the new holdings become available.